AIDS cases resulting from heterosexual transmission accounted for the largest proportionate increase in reported AIDS cases in the USA in 1996, making up 19% of newly diagnosed cases. A number of studies have focused on prevention for heterosexual women, but next to no research has been focused on heterosexual men, a serious gap in efforts to prevent heterosexual transmission of HIV. This study will recruit a random sample of 500 adult heterosexually-active men, living in neighborhoods with significantly higher than county-average STD rates. Using survey research and biological markers of STDs, we seek to better understand men's decision making with regard to STD/HIV prevention behaviors. This will parallel data previously collected on at-risk heterosexual women from this community. The study will: 1) Describe heterosexual men's beliefs, attitudes, self- efficacy, perceived norms and behavior with regard to three STD/HIV protective methods: abstaining from penetrative intercourse, being in a mutually monogamous relationship, and using male or female condoms; 2) test the adequacy of the traditional Theory of Reasoned Action (TRA) to model men's intentions and behavior with regard to each of these three methods; 3) test the TRA sufficiency hypothesis, which contends that all other variables that affect intention and behavior are mediated by the TRA variables of attitude and/or social normal, using an expanded model that adds intrapersonal, interpersonal, and sociocultural variables, not specified in the original model, as additional predictors of each of these three methods; 4) determine whether men form intentions toward each of the three protective methods independently (i.e., as a decision to use versus not use each method) or as a choice among alternatives (i.e., by comparing their intentions toward each method to each other); and 5) test the effect of learning about one's STD status (using biomarkers of disease) on intentions to use each of the protective methods and on subsequent behavior. The study will examine unique aspects of heterosexual relationships by examining the role of men's motivation for pregnancy and the importance of traditional, culturally prescribed male gender role beliefs in their decision making.